Abrasive blast cleaning system

ABSTRACT

An abrasive blast cleaning system includes a blast chamber for blasting sand from a casting in a no-bake mold with the removed sand and spent abrasive thereafter being separated in an air wash separator.

United States Patent Rowe 1 1 Sept. 12, 1972 [54] ABRASIVE BLAST CLEANING SYSTEM [72] Inventor: Russell L. Rowe, Hagerstown, Md.

[73] Assignee: The Carborundum, Niagara Falls,

[22] Filed: Oct. 30, 1970 [21] Appl. No.: 85,645

[52] US. Cl ..5l/9

[51] Int. Cl ..B24c 3/08 [58] Field of Search ..l64/5, 131, 344; 5l/8,9, 14, 51/15, 5;24l/DIG. 10

[56] References Cited UNITED STATES PATENTS 1,954,111 4/1934 Wilks ..5 H8

2,239,714 4/1942 Hammell ..5 H9 2,261,947 1 l/l941 Bamebl et al. ..164/5 3,055,150 9/ 1962 Greenberg et al. ..5 H14 3,368,677 2/ 1968 Bradley ..209/135 FOREIGN PATENTS OR APPLICATIONS 144,072 11/1951 Australia ..51/320 539,527 4/1957 Canada 1 64/5 Primary Examiner-Donald G. Kelly Attorney-Robert E. Walter and David E. Dougherty [57] ABSTRACT An abrasive blast cleaning system includes a blast chamber for blasting sand from a casting in a no-bake mold with the removed sand and spent abrasive thereafter being separated in an air wash separator.

3 Claims, 1 Drawing Figure Abr'as ive Collect Sand PKTENTED I973 3.690.066

Abras we 52 C0llect Fines Collect Sand ABRASIVE BLAST CLEANING SYSTEM BACKGROUND OF INVENTION A recent development in the casting industry is the use of chemical bonded molds. Essentially, this practice utilizes quality sand, a chemical binder and a catalyst which are mixed together and hardened into a solid cake at ambient temperatures. Accordingly, baking is not required for such molds and the practice is, therefore, known in the art as no-bake molding. Generally, the base binder used in no-bake molding is either an acid base such as a chemical binder with phosphoric acid as the activator or is an oil base. In practice the no-bake mold pattern is disposed in a topless frame on, for example, a support table with the no-bake ingredients being added to form a'cavity corresponding to one portion of the casting and with rigidifying rods added thereto. The mold is then inverted and the complementary portion of the no-bake mold is formed thereon so that the resultant composite cavity corresponds to the casting. Suitable gating is of course also provided; This practice is generally similar to standard foundry techniques but thus differs in at least one major respect, namely, the no-bake molding equipment does not require a heavy flask in which to house the sand when the molten metal is subsequently applied to the cavity. Even the topless frame used initially in the process is not needed during the casting forming step.

The no-bake molding process potentially represents a significant advancement in the foundry art since it offers a number of distinct advantages. For example the molds are easier to make without requiring a skilled molder. There is a cleaner environmentwith less dust and spillage than with green sand molding. The nobake technique is quicker since jolt mechanisms are not required. Simple form boxes or topless frames are merely necessary to shape the mold rather than the conventional heavy flasks. The molds can be handled without breaking apart by providing a grid plate or strapping and thereby the mold with its casting can be moved to a shaker or cleaning process without breaking apart. It has been suggested that the mold shell or sand can be removed by blasting and in such case the mold shell and core can be handled to the interior of a blast machine where the sand and dust can be contained and shake out noise eliminated. Moreover, the casting finish is thereby improved and casting tolerances can be tightened with the castings matching the pattern. The castings can go directly to numerically controlled machines, thereby obviating the need for rough cuts on manual machines.

Despite, the numerous advantages such as indicated above which are possible with no-bake molding, there are a number of serious disadvantages which might cause this process to meet stiff acceptance by the foundry art. These disadvantages include the increased costs for quality grade sand which might cost three or four times more than the'cost of green sands. Since quality sand is used, this sand must be reclaimed for reuse to make the entire process economically feasible.

Although attempts are being made at reclaiming and reusing the sand, experts cannot agree on the percentage of reclaiming possible with a system nor the qualities needed or obtained by a system. The publication, Foundry, September 1970, pages 83-90, for example, describes one such attempt at sand reclamation. The

reclaimed sands with the present systems, however, are not uniform in qualities. In this respect the build-up of fines and/or organics seriously affects the molds using reclaimed sands. Moreover, proposed reclaiming systems require shakers, crushers or Muller type units which are noisy and dusty'and also require rather large floor space and head room with high maintenance and capital costs.

SUMMARY OF INVENTION An object of this invention is to provide an abrasive blasting system which removes the sand from the casting in a no-bake mold and subsequently separates the spent abrasive from the sand.

A further object of this invention is to provide such a system which effectively reclaims both sand and abrasive to such a high degree that each can be reused.

In accordance with this invention an abrasive blast cleaning system includes a blast chamber for blasting sand from a casting in a no-bake mold with the removed sand and spent abrasive thereafter being separated in an air wash separator.

The reclaimed abrasive may be conveyed directly back to, for example, centrifugal throwing wheels which are used in removing the sand from the casting. Lumps of sand in the mixture may be crushed prior to feeding the mixture into the separator to facilitate the separating action.

THE DRAWINGS The single FIGURE schematically illustrates the flow chart which includes the blast means and separating means in accordance with this invention.

DETAILED DESCRIPTION As shown in the drawings the abrasive blast cleaning system includes a blast chamber 10 with'a plurality of centrifugal throwing wheels 12 which project abrasive particles toward the interior of the chamber. Mounted above the chamber 10 is for example a monorail 14 which carries a frame 16 upon which is supported a nobake mold 18 containing a casting 20 embedded in sand 22. As is customary in this process rods 24 are also disposed in themold l8. Suitable means are provided to hold the casting 20 suspended when its supporting sand has been removed. This means may include for example a suspension member 26 connected to an extension on the casting.

As the abrasive particles strike the mold the sand is removed from the casting and falls toward the bottom 28 of blast chamber 10 along the spent abrasive. Generally, about three-fourths of the sand is in small granular form while about one-fourth is in large lumps. Thus the small granular sand, the large lumps, the rods 24, the spent abrasive and fines and other contaminants fall to the bottom28 of blast chamber 10. In order to make the no-bake molding process economically feasible it is essential that these various elements be separated so that for example the sand and also the abrasive particles may be reused.

From the bottom 28 of chamber the various collected elements are ultimately conveyed to a separator 32. Prior to being inserted in the separator, however, the rods 24 are removed and the lumps are crushed by any suitable crushing means 30. In the meantime the abrasive particles projected from blast wheels 12 continue to strike the casting so that the casting is cleaned. Thus the single installation is used not only for removing the no-bake sand from the casting but also for cleaning the casting.

As schematically shown in the drawing the mixture which contains abrasive particles, granular sand, fines and other contaminants is conveyed to separator 32. In accordance with this invention separator 32 is of the air wash type such as shown and described in U. S. Pat. No. 3,368,677 the details of which are incorporated herein by reference thereto. In general this separator works onv the principle of subjecting a falling mixture to an air curtain so that the components of the mixture are diverted into individual streams depending on the weight of the particular components. This separation into individual streams is facilitated by the inclusion of skimmer plates in the separating chamber with the number of skimmer plates being determined by the number of streams desired. As shown in the drawing, for example, the air curtain is blown in through inlet 34 and exits through outlet 36 after passing through separating chamber 38. Skimmer plates 40 are provided in the path of flow of the air curtain so that the falling mixture 42 is divided into individual streams. Since the abrasive particles are the heaviest components of the mixture these particles are the least affected by the air curtain and thereby fall generally straight downward through outlet 44. The next heaviest elements are the sand granules which are slightly diverted by the air curtain and fall through outlet 46 for collection at station 48. Outlet 50 is provided for discharging the fines into collector 52, while dust and other light-weight contaminants are discharged through outlet 36 which in turn may communicate with a suitable dust collector (not shown).

It has been found that the provision of the air wash separation 32 is so effective in conjunction with the use of abrasive blast means for no-bake sand removal, that the collected abrasive particles may be recycled back to the individual throwing wheels 12. Moreover, the collected sand is substantially pure and free of these abrasive particles and of the fines and other contaminants and the collected sand is also in condition for reuse in a further no-bake molding process.

What is claimed is:

1. An abrasive blast cleaning system comprising a blast chamber, means for supporting a no-bake mold in said chamber with the mold containing a casting embedded in sand, abrasive blast means for directing abrasive particles against the mold to remove the sand from the casting, means for collecting the mixture of removed sand and spent abrasive particles, a separator, means for conveying the mixture to said separator, means between said blast chamber and said separator for granulating lumps of the sand in the mixture before said feed means drops the mixture into said separator for facilitating the separation action, said separator being of the air wash type with a separating section and means for bl iwing an air curtain through said separating section, eed means for ropplng e mixture into said separating section to be subjected to the air curtain while falling through said separating section, skimmer plate means and said separating section to divide the falling mixture into individual streams of sand and of abrasive particles, and collecting means connected to the bottom of said separating section for collecting the individual streams of sand and of abrasive particles distinct from each other, and recycle means for transporting the collected abrasive particles from said collecting means back to said abrasive blast means.

2. In the system of claim 1 wherein said support means includes a skeletal frame mounted on a monorail.

3. In the system of claim 2 wherein said abrasive blast means are centrifugal throwing wheels, and said collecting means further includes a fines collection hopper. 

1. An abrasive blast cleaning system comprising a blast chamber, means for supporting a no-bake mold in said chamber with the mold containing a casting embedded in sand, abrasive blast means for directing abrasive particles against the mold to remove the sand from the casting, means for collecting the mixture of removed sand and spent abrasive particles, a separator, means for conveying the mixture to said separator, means between said blast chamber and said separator for granulating lumps of the sand in the mixture before said feed means drops the mixture into said separator for facilitating the separation action, said separator being of the air wash type with a separating section and means for blowing an air curtain through said separating section, feed means for dropping the mixture into said separating section to be subjected to the air curtain while falling through said separating section, skimmer plate means and said separating section to divide the falling mixture into individual streams of sand and of abrasive particles, and collecting means connected to the bottom of said separating section for collecting the individual streams of sand and of abrasive particles distinct from each other, and recycle means for transporting the collected abrasive particles from said collecting means back to said abrasive blast means.
 2. In the system of claim 1 wherein said support means includes a skeletal frame mounted on a monorail.
 3. In the system of claim 2 wherein said abrasive blast means are centrifugal throwing wheels, and said collecting means further includes a fines collection hopper. 